March 18, 2014

The Search For Water On Two Planets

By studying the behavior of groundwater at different densities, a team of Australian scientists is hoping to help with the study of water on other planets, as well as water conservation strategies here on Earth.

The team is currently working on the theory that groundwater runs faster whenever it contains salt, heat, radioactive waste or polluted fluids from landfills – all of which raise the water’s density and therefore the speed it moves downwards. A newly published study appearing in the Journal of Geophysical Research is based on this concept and applies the theory to the cycle of freezing and thawing that appears to be taking place on the Martian surface.

“The search for water on Mars is part of the search for life, which requires water to survive,” said Craig Simmons, a researcher at Australia’s National Centre for Groundwater Research and Training (NCGRT) who was not directly involved in the new study. “Various studies as well as spacecraft and satellite observations hint that water exists beneath Mars’s icy crust, and in this latest study, the scientists have found evidence of water – in the form of ice and brine – at its equator.”

“As the subsurface temperatures of the Red Planet are above the melting point of water, water exists as liquid beneath the ground,” he added. “The scientists speculate that this warm water travels up from the depths of Mars to the surface, bringing salt with it as it rises. It then freezes due to the extreme cold.”

On Earth, Simmons said, very similar density effects can be observed when seawater encroaches into coastal aquifers, when polluted water runs away from landfills, when radioactive waste seeps out of underground storage facilities, in geothermal energy creation and deep carbon sequestration, and in the action of groundwater beneath salt lakes.

“When a heavier groundwater layer sits on top of a layer of clean fresh water, it will sink because of gravity,” he said. “Similarly, warmer water that’s less dense than cold water rises to the top. This rapid mixing caused by varying water densities appears to drive groundwater much faster than previously thought.”

“These density-driven groundwater flows can be found around the world,” he continued. “They’re fundamental to many areas of hydrogeology, and are critical for scientists’ understanding and prediction of the occurrence, distribution, movement and quality of groundwater on Earth.

“For instance, we can model where and how fast contaminated or saline water will travel, and so try to prevent it from polluting nearby fresh aquifers which people rely on for drinking or domestic use,” Simmons said. “This is vital to securing the Earth’s fresh water supplies, especially in heavily populated regions like China, India, the Middle-East and North America where they are already greatly stressed.”

“This density-driven groundwater flow is critical on Earth, so it’s fascinating to see the theory being applied on Mars,” Simmons concluded, referring to the newly released study. “It shows that the flow is more important than we thought – even on other planets – and improves our knowledge on how groundwater behaves. It’s very exciting indeed!”